The long term goal of this proposed research is to elucidate the regulation of the rat LH receptor gene. The immediate objectives are to define the promoter region and to identify regulatory elements in this gene. Evidence for the critical roles of LH, hCG and their receptor in female reproductive physiology is compelling. A failure in expression of these hormones or the receptor will results in no ovulation and no pregnancy, leading to infertility. Transcription of the LH receptor gene can be induced by FSH or cAMP/estrogen and the expressed receptor can be suppressed by LH/hCG. Genes that are not only inducible but also suppressible are interesting as is the LH receptor gene. because they are likely to be involved in the switching mechanisms of important biological processes. Studies on these hormone-dependent inducibility and suppressibility could reveal novel enhancer and suppressor elements and will serve as a model for other protein hormone receptors. Understanding transcriptional control necessitates the identification of regulatory elements. Our preliminary study suggests that [1] a single gene encodes the rat LH receptor, [2] 11 exons are present In the coding region, [3] there are a sequence similar to the ERE. an exact and several homologous AP-2, and a G-rich CRE. but no consensus CRE, and [4] there are variant receptors that appear to be produced by alternate splicing. These results serve as the basis for proposed studies concerning the following major goals. 1. We will determine the size and restriction map of the entire gene, the transcription start-sites and the boundaries of an apparent intron in the 5'UTR. 2. The cAMP- and estradiol-responsive enhancer elements and LH-responsive suppressor elements in the rat LH-R gene will be identified and verified. 3. We would like to determine whether FSH- or cAMP/estradiol-induction of LH receptor transcription is direct or requires de novo protein synthesis. 4. We plan to characterize variant mRNAs which expect to produce a soluble form of receptors without a transmembrane domain. These soluble receptors may play important roles in the regulation of the hormone concentration in serum.